The second Mariner '69 spacecraft, Mariners VII, will be launched on fly-by missions to Mars on Monday, March 24, at about 2 p.m. The first spacecraft Mariner VI, was launched February 24.

A press room will be open at 1 p.m., Monday, for launch, at JPL in the Von Karman auditorium.

The first spacecraft will arrive at Mars on July 30, the second on August 4. The purpose of the flights is to determine if the Martian environment is suitable for life. The flights will determine if life exists on Mars.

The following Public Information people will be available during the mission:

region of the Me across the edge of the South Polar cap.

The Mars-to-Earth distance at the time the Mariners reach Mars is about 60 million miles--the distance differing slightly during the five-day interval. The science information gathered, as well as measurements indicating the condition of the spacecraft themselves, is transmitted to the huge ground antennas of the NASA-JPL Deep Space Network.

A few minutes after Mariner makes its closest approach to the planet, it will disappear behind Mars for nearly a half- hour, cutting off the radio signal from the spacecraft to Earth. The trajectories of both spacecraft were designed this way to permit a radio occultation experiment.

While entering and exiting the radio blackout area, Mariner's signal is affected by its passage through the Martian atmosphere. Analysis of this effect as received on Earth will result in a determination of the pressure and density of the atmosphere.

A final experiment, celestial mechanics, will use tracking information to refine astronomical data.

Each Mariner carries two tape recorders which store the TV pictures and measurements taken by the other science instru- ments during the close passages of Mars. As the Mariners fly past the planet, the recorders are played back over the radio link to Earth. Two complete playbacks from each spacecraft will take just less than three days. The Mariners then continue in their perpetual orbits around the sun.

At launch time for Mariner G tomorrow, Mariner 6 will be about 4.9 million miles from Earth and traveling at a velocity of 6790 miles per hour relative to Earth. Its flight path is 226 million miles long and duration of flight from Earth to Mars is 156 days.